Infection is a catastrophic and too frequent complication of many surgical procedures. In the case of surgical procedures that introduce a foreign substance into the body, there is increased risk of such infection that leads to failure of the surgical procedure or dangerous infections in the body. For example, in spinal surgery several existing measures to prevent infection are only partially successful, despite the best interests and intentions of medical professionals. Spinal surgical sites are prone to bacterial colonization due to hardware presence, long surgical times, and the creation of a “dead” space (≥5 cm3) that is filled with wound exudate. Following trauma, there is both immune suppression and polymicrobial contamination with an accompanying increase in infection risk.
Importantly, bacteria that are adherent to spinal hardware or in floating biofilms in wound fluid become recalcitrant to antibiotic therapy7,8. Despite aggressive peri-operative antibiotic treatments, between 1 in 20 and 1 in 100 patients undergoing spinal surgery develop an infection. Hardware removal and implantation of an antibiotic spacer is not possible in spinal infection, requiring treatment in the presence of hardware. Because spinal infections must be treated in the presence of the hardware, the current standard of care includes irrigation, aggressive debridement of the infected soft tissues, and prolonged antibiotic treatment, often resulting in extended pain, delayed wound and bone healing, disability, and, in the worst cases, death.
One method to minimize infection is for spinal surgeons to place ˜1 g of vancomycin (VAN) during closure1-4 thereby lowering morbidity and mortality and saving ˜$35 k-114 k/affected patient5, 6. Importantly, these infections are assumed to be caused by adherent bacteria which are markedly recalcitrant to antibiotic treatment9,10, thus the use of supratherapeutic levels of VAN peri-operatively. However, the efficacy of this practice is currently unclear. Even with high VAN levels, decreases in spinal infection rates are only modest. Perhaps because VAN is active against only Gram-positive pathogens3 such as S. aureus, VAN packed around the implant prior to closure may1,2,4 or may not3 decrease contaminating bacteria. Thus, despite this aggressive prophylaxis with VAN3, ˜1-4% of spinal surgeries may still become infected.
Spinal infection rates are >4%. After the surgical site has been closed and prophylactic antibiotics are depleted; surgeons do not currently have a means to locally continue prophylaxis to combat establishment of these infections. Other treatment choices are limited as debridement of the spine to remove adherent bacteria cannot be undertaken, local antibiotic injection could introduce additional bacteria, and antibiotic-eluting spacers have not been developed for spinal applications.
Therefore a focus on new ways to create implant systems that prevent bacterial colonization is essential. Furthermore to be most effective, new treatments must eradicate pathogens before their adherence to the implant surface attenuates antibiotic effectiveness and immune susceptibility. The work in this application addresses this need for a simple device to continue prophylaxis and to lower the infection rates associated with spinal fusions.